1. Field of the Invention
The present invention relates to a conveyance apparatus for conveying a sheet, which is drawn out from a roll sheet, by a conveyance roller.
2. Description of the Related Art
Some types of image forming apparatuses can use A2 or larger size continuous sheets. In such image forming apparatuses, a roll sheet in which the continuous sheet is wound on a paper tube is commonly used.
As a state of an end portion of the roll sheet, one type of roll sheet in which the end portion thereof is not fixed to the paper tube is provided. In this type of roll sheet, the paper tube alone can make idle rotation. The state in which the paper tube alone can make idle rotation is referred to as a “separation state”. Further, there is another type of roll sheet in which an end portion thereof is fixed to the paper tube with a tape. In this type of roll sheet, there is a case where the roll sheet cannot be fed from a feeding unit. The state in which the end portion of the roll sheet is not separable from the paper tube is referred to as a “non-separable state”. In the non-separable state, the roll sheet is pulled by the feeding unit and a conveyance unit that is disposed on the downstream side of the feeding unit. If a printing operation is continued in this situation, there is a problem in which the printing operation is repeatedly executed on the same place of the roll sheet.
Japanese Patent Application Laid-Open No. 2009-269713 discusses a configuration for determining whether the roll sheet is in a non-conveyable state in which the end portion thereof is fixed to a roll sheet shaft, by changing a driving condition of a roll sheet driving unit when a detection unit detects that the roll sheet is close to the end portion thereof.
In Japanese Patent Application Laid-Open No. 2009-269713, when it is detected that the roll sheet is close to the end portion thereof, a motor for driving the roll sheet shaft is driven in a rewind direction. In the case where a moving amount of the roll sheet is not a proper value, the roll sheet is determined to be in a non-separable state. Since the configuration discussed in Japanese Patent Application Laid-Open No. 2009-269713 cannot make the determination without driving the motor in the rewind direction, the printing operation has to be suspended, and thus, it is problematic in that productivity of the printing apparatus is lowered.